Pulse oximetry utilizes a noninvasive sensor to measure various physiological parameters, such as oxygen saturation (SpO2) and pulse rate of a person. The sensor has light emitting diodes (LEDs) that transmit optical radiation of various wavelengths into a tissue site and a detector that responds to the intensity of the optical radiation after attenuation by pulsatile arterial blood flowing within the tissue site. Pulse oximeters have gained rapid acceptance in a wide variety of medical applications, including surgical wards, intensive care and neonatal units, general wards, home care, physical training, and virtually all type of monitoring scenarios.
Pulse oximeters capable of reading through motion induced noise are disclosed in at least U.S. Pat. Nos. 6,770,028, 6,658,276, 6,584,336, 6,263,222, 6,157,850, 5,769,785, and 5,632,272, which are assigned to Masimo Corporation (“Masimo”) of Irvine, Calif. and are incorporated by reference herein. Low noise pulse oximetry sensors are disclosed in one or more of U.S. Pat. Nos. 7,027,849, 6,985,764, 6,934,570 6,760,607 6,377,829 6,285,896 5,782,757 5,638,818, which are also assigned to Masimo and incorporated by reference herein. Moreover, pulse oximeters capable of reading through motion induced noise and low noise optical sensors including LNOP® disposable, reusable and/or multi-site sensors and Radical®, Rad-5™, Rad-8™, Rad-9™, PPO+™, and Pronto-7™ monitors are also available from Masimo.
Multiple parameter monitors and multiple wavelength sensors are described in U.S. patent application Ser. No. 11/367,033 entitled Noninvasive Multiple Parameter Patient Monitor filed Mar. 1, 2006 and U.S. patent application Ser. No. 11/367,013 entitled Multiple Wavelength Sensor Emitters filed Mar. 1, 2006, incorporated by reference herein. Multiple parameter monitors are capable of measuring various physiological parameters, such as oxygen saturation (SpO2), hemoglobin (Hb), oxyhemoglobin (HbO2), total hemoglobin (SpHb™), carboxyhemoglobin (SpCO®), methemoglobin (SpMet®), total oxygen content (SpOC™), perfusion index (PI), pleth variability index (PVI®), pulse rate (PR), and temperature. Moreover, multiple parameter monitors and multiple wavelength sensors including Rad-57™ and Radical-7™ monitors and Masimo Rainbow® brand adhesive and reusable sensors are available from Masimo. MS-brand processor boards incorporating SHARC® DSPs from Analog Devices, Inc. are also available from Masimo.
It has been discovered that variations in environmental conditions, such as atmospheric pressure, altitude, humidity, temperature, and the like can affect the readings of the physiological parameters by the pulse oximeter and multi-parameter monitors. Thus, varying environmental conditions can cause a pulse oximeter and/or a multi-parameter patient monitor to be less accurate.